Australian researchers found that the embryos could identify electric fields simulating a nearby predator, despite being confined to a tiny egg case.
Australian researchers found that the embryos could identify electric fields simulating a nearby predator, despite being confined to a tiny egg case.

Embryonic sharks play dead to evade predators

Brown-banded bamboo sharks can sense electrical fields even before they've hatched from their egg cases.

Despite being confined to the small space within the egg case, where they are vulnerable to predators, embryonic sharks are able to recognise dangerous stimuli and react with an innate avoidance response.

Normally, an embryo pulses its gills actively. But when researchers turned on electrodes to produce an electric field near the egg cases, the unhatched sharks froze and stilled their gills for several seconds.

Why is Scientific Diving Safer?

Scientific diving appears to be one of the safer forms of diving, a recent study of incidences of decompression illness over ten years has found. This safety seems to be facilitated by a combination of relatively high levels of training and oversight, the predominance of shallow, no-decompression diving and, possibly, low peer or institutional pressure to complete dives under less than optimal circumstances.